I was sitting there thinking "why did Subaru say that the rear diff was changed to a Torsen diff for 2007 if there is no actual difference? Thanks for confirming that.

They changed the rear diff to a DIFFERENT helical/mechanical, and the new one happens to be made by Torsen, which is a big name in the field and as far as I know (which is NOT very far) was one of the first companies to develop mechanical LSDs for performance applications. I know Lancia and Audi had them on their hot AWD cars of yesteryear, and they were what the Group B cars ran.

I wish there were a book with very many, extremely large, colorful pictures, that explained all about diffs for performance applications.